<html xmlns="http://www.w3.org/1999/xhtml" xmlns:math="http://www.w3.org/1998/Math/MathML">
<head>
<script>

function boom()
{
  var ms = document.createElementNS("http://www.w3.org/1998/Math/MathML", "ms");
  var textNode = document.getElementById("emptyset").firstChild;
  var mrow = document.getElementById("mrow");

  ms.appendChild(textNode); // *move* the text node from one place to another!
  mrow.appendChild(ms);
}

</script>
</head>

<body onload="boom();">

<math xmlns="http://www.w3.org/1998/Math/MathML">
<merror><emptyset id="emptyset">
  <mrow id="mrow"></mrow></emptyset></merror>
</math>

</body>

</html>
